Determining air leakage

Abstract

A system (100) and method for determining the air leakage of a space (102) in a building is disclosed. The system (100) comprises a processor (120); a source (130) of compressed air; a pressure sensor (150) configured to measure the pressure of air residing within the space (130) and to provide background pressure signals to the processor (120); a nozzle unit (140) for metering the supply of a pulse of compressed air from the source (130) and for directing the pulse into the space (102) and a source pressure sensor (132) configured to measure a transient pressure during the pulse and to provide a transient pressure signal to the processor (120), wherein the processor (120) is configured to determine the air leakage based on changes in the background pressure signals and from the transient pressure signal. This provides a more reliable and cost effective way of measuring air leakage.

The invention claimed is: 
     
       1. A system for determining the air leakage of a space in a building, said system comprising:
 a processor; 
 a source of compressed air wherein the source is a pressure tank containing compressed air, where a minimum size of the pressure tank is selected such that a quasi-steady pulse can be generated; 
 one or more space pressure sensors configured to provide transient pressure signals and background pressure signals of air residing within the space and, and to provide these signals to the processor; 
 a temperature sensor configured to measure the temperature of air residing within the space, and to provide a space air temperature signal to the processor; 
 a nozzle unit for metering the supply of a pulse of compressed air from the source and for directing the pulse into the space the nozzle unit configured to gradually reduce a constriction of flow of air from the source as it leaves the source such that it produces a reproducible pulse shape and delivers quasi-steady flow conditions; and 
 a source pressure sensor configured to measure a transient source pressure during the pulse and to provide a transient source pressure signal to the processor;
 wherein the background pressure signals are pressure readings of internal pressure of air within the space before and after supply of the pulse; and the transient source pressure signals are pressure readings of internal pressure of air within the space during the quasi-steady flow conditions created by the pulse; and 
 wherein the processor is configured to determine the air leakage based on: a volume of the space; changes in the background pressure signals; the transient space pressure signal, the space air temperature signal, the transient source pressure signal and the volume of the source. 
 
 
     
     
       2. The system according to  claim 1 , wherein the system further comprises a reference pressure source for providing a reference pressure reading. 
     
     
       3. The system according to  claim 2 , wherein the reference pressure source is an external space, separate from the building. 
     
     
       4. The system according to  claim 2 , wherein the reference pressure source is a reference pressure tank having a known volume and pressure of air. 
     
     
       5. The system according to  claim 2 , wherein the system further comprises a reference pressure sensor for recording a transient reference pressure signal of the reference pressure source. 
     
     
       6. The system according to  claim 1 , wherein the nozzle unit comprises an outlet for delivering the pulse into the space and a valve connection between the outlet and the pressure tank. 
     
     
       7. The system according to  claim 6 , wherein the outlet is a pneumatic silencer for controlling expansion of the pulse of compressed air into the space. 
     
     
       8. The system according to  claim 6 , wherein the valve connection is a solenoid valve. 
     
     
       9. The system according to  claim 6 , wherein the valve connection is an automated valve. 
     
     
       10. The system according to  claim 6 , wherein the outlet has a 1 inch diameter at its external edge. 
     
     
       11. The system according to  claim 1 , wherein the nozzle unit opens for a period of time required to provide a desired volume of the pulse. 
     
     
       12. The system according to  claim 11 , wherein the pulse metered by the nozzle unit has a volume more than 0.003% and less than 0.5% of the volume of the space. 
     
     
       13. The system according to  claim 11 , wherein the nozzle unit supplies a pulse of 1.5s duration starting at 10 bar pressure. 
     
     
       14. The system according to  claim 1 , wherein the nozzle unit is configured to gradually reduce the flow constriction of the pulse from the source to the space. 
     
     
       15. The system according to  claim 14 , wherein the source pressure sensor records a series of transient pressures to determine a mass flow of air out of the source during supply of the pulse. 
     
     
       16. The system according  claim 1 , wherein the system further comprises a compressor for providing and/or maintaining the source of compressed air. 
     
     
       17. The system according to  claim 1 , wherein the system further comprises a control unit for controlling the metering of the supply of the pulse from the source. 
     
     
       18. A control unit for determining the air leakage of a space in a building, said control unit comprising one or more systems according to  claim 1  and configured to control the metering of the supply of the pulse from the source. 
     
     
       19. A control unit according to  claim 18 , wherein the control unit integrates one or more components of the system within the control unit. 
     
     
       20. A method of determining the air leakage of a space, said method comprising the steps of:
 measuring a background pressure of air residing within the space, indicative of background pressure variations within the space; 
 measuring a temperature of air residing within the space; 
 displacing a volume of compressed air from a source into the space using a nozzle unit to direct a pulse of pressurized air, the nozzle unit configured to gradually reduce the constriction of flow of air from the source as it leaves the source such that it produces a reproducible pulse shape and delivers quasi-steady flow, wherein the source is a pressure tank containing compressed air, selected with a minimum size such that the pulse shape and quasi-steady flow can be produced; 
 measuring transient pressure of air within the space during quasi-steady flow conditions created by the pulse; 
 determining an injection pressure of the pulse as it is directed into the space; 
 measuring an altered background pressure of air residing within the space after dissipation of the pulse; 
 determining a background pressure variation based on the background pressure and the altered background pressure; and 
 determining a leakage profile of the air filled space using the injection pressure, the volume of the source, the initial air temperature within the space, the transient pressure of air within the space, the background pressure variations and the internal volume of the space. 
 
     
     
       21. The method of  claim 20 , wherein the step of determining an injection pressure further comprises the step of: obtaining the change in internal pressure of the space during at least a portion of the pulse. 
     
     
       22. The method of  claim 20 , wherein the step of determining a background pressure variation further comprises the step of: interpolating a transient background pressure of air during the pulse of pressurized air from the background pressure of air and the altered background pressure of air. 
     
     
       23. The method of  claim 22 , wherein the step of determining a leakage profile further comprises the step of adjusting for the transient background pressure. 
     
     
       24. The method of  claim 20 , further comprising the step of extrapolating the leakage profile to determine the likely leakage of air leakage from the space at elevated air pressures.